Planarity-Engineered 1,2,3-Triazole-Based 1D Covalent Organic Frameworks for Enhanced Visible-Light Photocatalytic C-3 Thiocyanation of Indoles

Covalent organic frameworks (COFs) have emerged as efficient metal-free photocatalysts for green chemical synthesis and environmental remediation. However, their performance is often limited by interlayer π-π stacking, which hampers charge transport and active site accessibility. To address this challenge, we report two one-dimensional (1D) donor-acceptor COFs (PYTZ-COF and ETTZ-COF) featuring 1,2,3-triazole linkages and tunable optoelectronic properties through precursor rigidity engineering. Compared to ETTZ-COF, PYTZ-COF exhibits a reduced torsional angle, broader visible-light absorption, smaller exciton binding energy, and a narrower band gap, along with a significantly larger BET surface area (414 m²/g). These features facilitate efficient charge separation and accelerated interfacial electron transfer, as confirmed by photoelectrochemical analysis and DFT calculations. Under blue light irradiation, PYTZ-COF efficiently generates superoxide radicals (•O₂⁻), enabling selective C-H thiocyanation of indole derivatives. This study not only expands the structural diversity of 1D COFs but also introduces a general strategy for improving photocatalytic activity via molecular-level planarity modulation, offering new insights into the design of redox-active COFs for visible-light-driven environmental catalysis.